Fix issue #2102 and #2103

[yaxia]

1. Fix the issue that it reports: Cannot read property 'substr' of null when user doesn't login or no endpoint is provided.
2. Modify the build script as the npm.zip is only available in https address now.

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[yaxia]

The reason I change it is that at the day Node.js 4.0 was released, this npm cannot be downloaded from this address and the server returned HTTP 301 (Moved Permanently), only HTTPS worked. It looks like the address works again now, but I am not sure whether it will be inaccessible again.